Analysis of infinite arrays of arbitrarily shaped planar radiating elements using a Floquet mode based Method of Moments approach

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Abstract

Large phased array antennas are theoretically capable of delivering the directive
gain of similarly sized aperture antennas while offering electronic beam scanning
capabilities and greater operational flexibility. Unfortunately, the high cost associated with
large phased antenna arrays has limited their use to highly specialized applications where
no other antenna system configuration is possible. The recent development of less
expensive microwave active devices has led to a renewed interest in large phased antenna
arrays. These devices allow the amplification and signal processing required in phased
antenna arrays to be distributed among many identical modules which combine the
amplification, feed network, and radiating element sections of traditional antenna arrays.
These modules can then be produced at a lower unit cost and result in an antenna system
which is more easily integrated and repaired.

The practicality of large phased antenna arrays is still limited by the great difficulty
experienced in predicting their performance. Mutual coupling effects between the
radiating elements produce significant variations from ideal array theory. The prediction
and reduction of these effects requires a characterization approach which is computational
rather than experimenta1. This document presents a new approach which allows the
characterization of arbitrarily shaped planar radiating elements printed on a dielectric support slab backed by a perfect electric conductor ground plane. This analysis approach
uses a Method of Moments technique to determine the electric current distribution over a
set of bi-triangular sub-domain elements describing a single radiating element. The effects
of mutual coupling in the fully active infinite antenna array are included in the analysis by a
Floquet mode based Green's function used in the Method of Moments analysis. This
characterization technique has been implemented in the computational electromagnetics
code ASIA (Analysis Software for Infinite Arrays), The analysis approach presented here
is validated by comparison with published input impedance data for two different radiating
elements. Finally, preliminary analysis results are shown for a more complex radiating
element.